1. Field of the Invention
The present invention relates to a manufacturing method for a heavy-duty tire and a tire manufactured by the same, and more particularly to a method for manufacturing a heavy-duty pneumatic tire by winding a reinforcing belt disposed in a belt layer of a tread with an untopped spiral steel cord, and a tire manufactured by the same.
2. Description of the Related Art
Recently, commercial vehicles such as a truck have been reducing height of a platform thereof in order to increase a loading space. According to this, there is a growing tendency to reduction of an outer diameter of a tire.
In addition, considering a fuel ratio of the vehicle, there have been made diverse efforts for reducing weight of the vehicle, one of which is a single tire comprising a single wheel instead of a dual wheel mounted to a commercial vehicle. Such a single wheel tire is so called a super single type tire, which is capable of not only reducing the weight of the tire but also reducing the number of required rims, accordingly helping reduce the vehicle weight.
The super single type tire has an even greater width and a lower aspect ratio than general heavy-duty tires. Due to the low aspect ratio, various members of the tire, especially a carcass and a belt, are subject to greater inner pressure and load, thereby deteriorating durability of the belt of the tire.
Furthermore, in case of inflation of the tire, an outer diameter of a tread center part is more increased than an outer diameter of a shoulder part. Therefore, a grounding portion is concentrated on the tread center part, which may cause deformation of the tread center part. Since such deformation deteriorates the durability of the belt as well as lifespan of the tire, there is an increasing need for reinforcing the tread.
Conventionally as well, structures of a reinforcing belt layer applied to a belt part of a tread to reinforce various members have been suggested. For example, U.S. Pat. No. 6,357,527 introduces a tire with a reinforcing belt layer 104 formed by spirally winding a single strand of steel cord 106 between a second belt and a third belt attached to a forming drum 101 as shown in FIG. 5. Although the effect as a reinforcing belt can be obtained by this tire, the manufacturing cost is increased since excessive time is required to wind the single strand of steel cord 106 between belts of a belt layer of a wide-width tire.
To overcome the above problems, there was introduced another reinforcing belt structure as shown in FIG. 6, which reinforces a reinforcing belt layer 204 by spirally winding a steel strip 206 constituted by a plurality of steel cords on a forming drum 201, as disclosed in US Patent No. 2005-0126674-A1. However, since the steel strip 206 has wide cut parts on both ends thereof, stress is concentrated on the cut parts, thereby damaging the belt.